This invention relates to data processing systems and in particular to multi-processor data processing systems utilising a data-bus or highway in order to permit the processors in the system to communicate with each other and with memory stores within the system and with external devices.
One example of such a system is the Locus 16 data processing system. "Locus" is a Registered Trade Mark of the Marconi Company Limited.
Usually at least one of the processors in the system is capable of general purpose arithmetic and logical operations using a program stored within the system.
A problem which arises with such systems is that the processors commonly used are capable of generating only sixteen bits to form an addressing codeword giving access to requisite data stored in a particular part of a store and this limits the number of storage areas which may usefully be employed to 65,536(2.sup.16). For many purposes this is insufficient.
On the other hand, stores commonly have the facility to provide storage for of the order of 1,000,000 data items so as to be addressable by 20 bit words (2.sup.20) 1,048,576.
One object of the present invention is to provide an improved multi-processor data processing system in which the above difficulty is reduced.